I recently had passengers in the back of my Mazda 2 and the left hand seat belt has been fully extended and now does not retract at all. Looking into how I can remove the trimming so I can gain access to the bottom end of the belt. Am thinking I might need to remove the left hand seat.

 

there’s is quite a lot of posts on this forum about the rear seat belts going faulty.

 

WD40 with the long red tube, squirt in to the side of the reel.

 

Yes, this works.
I had the same problem.